The federal government is on track to release its study on whether natural gas drilling and hydraulic fracturing pollute drinking water in late 2014, the Environmental Protection Agency said Friday in a progress report on the closely watched analysis.

Although the update itself did not contain conclusions about the potential effects hydraulic fracturing could have on drinking water resources, it outlined the framework for 18 research projects already under way.

Critics have questioned the EPA's approach, which involves analysis of existing data from well sites around the country, computer modeling, laboratory studies and assessment of the toxicity of chemicals used in hydraulic fracturing fluids and drilling wastewater.

Hydraulic fracturing, credited with unlocking vast reserves of oil and natural gas nationwide, involves blasting sand, water and chemicals deep underground to open up the pores of dense rock formations and free fossil fuels trapped within.

Fears of water contamination from the chemicals pumped underground and the water that flows out of wells have accompanied a surge in horizontal drilling and hydraulic fracturing in Texas, North Dakota, Pennsylvania and other states.

The congressionally mandated study could be used as the foundation for future regulation and legislation governing hydraulic fracturing, now generally regulated at the state level.

The study is examining the relationship between water and hydraulic fracturing at almost every stage of the drilling process, from first acquiring water to use at wells to ultimately disposing of wastewater.

So far, agency scientists are scrutinizing data from seven sources, including information provided by nine hydraulic fracturing service companies, more than 300 well files supplied by oil and gas operators and thousands of chemical disclosure records filed on a voluntary registry known as FracFocus. The EPA also is looking at spill reports from Colorado, New Mexico and Pennsylvania to identify why fluids and wastewater were released.

The EPA said it is using computer modeling to evaluate how withdrawing large volumes of water in both dry and humid environments is affecting drinking water sources.

The agency said it is using computer modeling of six different scenarios to explore the likelihood that gas and fluid could migrate from deep shale formations to overlying aquifers. The EPA also said it is working to identify what conditions might be associated with the underground migration of gases and fluids to drinking water sources and is exploring the extent to which inadequately constructed wells, nearby natural faults and close man-made wells affect that movement.

The EPA also is investigating whether common municipal wastewater treatment processes are successful at removing harmful materials — including naturally radioactive elements pulled from the ground — in wastewater flowing from hydraulically fractured wells.

The American Petroleum Institute's upstream senior policy adviser, Stephanie Meadows, noted that a report by Battelle Memorial Institute, a not-for-profit research organization, released last summer called for more collaboration on the study between EPA and the industry. Meadows said the EPA has responded with some “constructive course corrections, including the formation of technical roundtables that include industry expertise.”

“More collaboration, continued transparency and stakeholder involvement are essential elements for any scientifically sound study, and we hope that the rest of this process remains open and any data released has the necessary context,” Meadows said.

But the environmental group Earthworks noted that EPA's report showed the agency had been unable to find a single company willing to test water quality at a site before and after drilling and fracturing.

“The EPA is being thwarted in perhaps the most important part of its study on fracking impacts,” the group said.